Input devices such as mice and joysticks to facilitate user input to a computer executing program code are well known in the art. A user manipulating an input device of this nature is able to interact with the software application being executed by the computer. Although these input devices are common, touch sensitive panels have also been considered to enable users to interact with software applications being executed by computers.
For example, U.S. Pat. No. 5,483,261 to Yasutake discloses an interactive graphics system including a touch-sensitive controller having a plurality of semi-transparent, light-diffusing panels imaged by a rear mounted video camera. The video camera is arranged to detect shadows on the panels caused by objects, such as fingers, in proximity to panels. The video camera output is conveyed to a computer having a monitor displaying a user controllable object. The program code executed by the computer processes the video camera output and updates the display to move the user controllable object in accordance with movement of shadows on the panels.
European Patent Application No. 0 554 492 to International Business Machines discloses an input device for optical input of commands or data to a computer. The input device includes a virtual keyboard within the field of view of a camera. Images captured by the camera are analyzed and interpreted to detect hand movements over keys of the virtual keyboard. Corresponding data input signals are generated by the input device and conveyed to the computer for processing.
U.S. Pat. No. 4,346,376 to Mallos discloses a touch position sensitive panel to overlie a cathode ray tube (CRT) and receive radiated light therefrom. The edges of the touch position sensitive panel are fitted with photodetectors to detect light trapped in the panel. When a user contacts the panel surface, light from the CRT becomes trapped within the panel by total internal reflection and is detected by the photodetectors. The output of the photodetectors is compared with the CRT raster position to determine the position on the surface at which contact is made.
U.S. Pat. No. 4,629,884 to Bergstrom discloses a touch sensitive key including a radiation-propagating prism disposed between a radiation source and a radiation detector. When a user contacts the top surface of the prism, radiation from the source that enters the prism is scattered towards a side surface of the prism and is detected by the radiation detector.
U.S. Pat. No. 4,710,760 to Kasday discloses a photoelastic touch-sensitive screen having light reflecting edges and light emitting/receiving modules at two corners of the screen. Light focused into the screen by the modules, propagates by internal reflection, reflects off the edges of the screen and is returned to the modules for absorption by circular polarizers. The polarization of light changes when the upper surface of the screen is contacted. The degree of change in polarization is dependent on the force applied to the upper surface of the screen. The change in polarization is detected by the circular polarizers allowing the position and force of contact on the upper surface of the screen to be determined.
Although the above-mentioned references disclose touch sensitive panels to detect user contact and generate corresponding output signals, improved touch sensitive panels to enhance user input capabilities are desired. It is therefore an object of the present invention to provide a novel human-machine interface and method for detecting contact between a surface and an object.